Method of reducing metal tubing



- Jan. 20, 1942; s. wEsTlN 2,270,398

` METHOD 0F REDUCNG METAL TUBING Filed' April '6, 1939 Y SL25 Sven Wesfr'n INVENTOR ATTORNEY.

Patented Jan.` 20, 1942 ME'rnoD or REDUCING METAL TUBING Sven Westin, West Allis,`Wis.

Application April s, 1939, serial No. 266,231

y 13 claims. (c1. 205;-8) This invention relates tothe art of reducing metal tubing. Industrial demands require metal tubing of various sizes ordinarily considerably below the' size at which the tubing issues from a tube iorming mill. This is particularly true of seamless steel tubing regardless of the type of forming mill or forming method employed in its'production. Y

The various tube forming mills and methods now employed are capable of producing tubing having walls of desired thickness, both as to degree and uniformity of thickness, but the problem of subsequently reducing both 'the external and internal diameters of the tubing' to desired sizes has not been solved to best advantage.

vide anew and more economical method of and means for reducing metal tubing,

Another object is toprovide a practical method for the hot drawing of metal tubing.

Another object. is to utilize a hot drawing method in the reduction of metal tubing.

Other more specific objects and advantages l f will appear', eitherexpressed or implied, from One tube reduction method now commonly 4 employed involves passing the formed tube in a hot condition through amultiplicity of aligned roll stands, each including a set oi coacting rolls forming' an orifice of less size than the preceding set and driven at an exact speed higher than the rolls of the preceding set. This equipment is not only very costly, but any departure from true alignment or proper roll speed, in any of the multiplicity of stands, results, in defective tubing and is the cause of much waste. Fui'-,

thermore, when operated under most favorable conditions, both ends of each length of tubing,

thus reduced, are always defective and end sections of substantial length must be cut off and discarded, causing further waste.

Another known method of tube reduction in-l volves the use of a sci-called draw-bench by which the tubing is drawn in a cold condition l through a die. This method is time consuming and expensive, not only because it requiresre.-

peated draws through dies of different sizes, but Y also because it also requires annealing and pick ling of the tubing before and after each draw. It is possible, however, by thisdraw-bench method, toA reduce the tubing to sizes smaller than are obtainable by the hot rolling reduction meth-y ed just described, and the prlxriary use of the draw-bench method is, as an adjunct to the hot rolling method, in furtherreducing the tubing after it has been reduced as far as ypossible by the hot rolling method. f l As heretofore practiced, the draw-bench method requiresthat the tubing be ,drawn cold. If attempted tofdraw hot tubing .through 'a die, there is a tendency for the tubing to neck or collapse as it issues from the die, due largely to the tension involved in the drawing process.

thefollowing description of a method which I have successfully employed in reducing metal tubing. t v

In the accompanying drawing:

Figure 1 is a longitudinal sectional view illustrating more or less diagrammatically one desirable arrangement for accomplishing the objects of this invention.

Y Figs. 2 and`3 are transverse sectio al views taken. along the lines 2-2 and 3- respectively, of Fig. 1.

Fig. 4 is a view of the parts shown in Fig. 1 in the relative positions occupiedpreliminary to starting a drawing operation.

Fig.` 5 is a perspective view cfa prepared tube end. V

The method selected for illustration and explanation involves the use of a die I0, constituting an element of a draw-bench of a Well known type, equipped with the usual draw head (not shown) adapted for gripping engagement with -the leading` end a f the tube b, and by which the tube is drawn through the die I0. A bar Il within the tube b makes it possible to draw the tube through the die I0` while the ing," as it issues from the die I0. vThe bar Il also assists the tube through the die lIl) by sustaining and transmitting a portion of the pulling force applied by the draw-head. The minimum clearance between the bar il and .the die orifice 'I2 is preferablyl not less than'the wall thickness of the tube b, so as to-avoid objectionable pinching of the tube between the bar and die.

The perimeter of the die orificeI I2 is considerably less than the normal perimeter of the'origi-v nal tube, so lthat va material and substantial re` duction is effected by passing the tube through the die I0. The die orifice I2 however is preferably non-circular so as to impart a non-circular form to the tube, and the bar II is preferably circular, so that, as the tube issues from the die it bears against the bar along peripherally spaced zones thereon.

It will be noted, upon reference to Fig. 2, that in the particular die shown at I the orice I2 thereof is of substantially oval or elliptical form, having a major horizontal axis of slightly less length than the diameter of the original tube b and a minor vertical axis of considerably less length than the diameter of the original tube, so that the tube in passing through that orifice is greatly reduced, the cross-sectional area of the reduced section c being less lthan half of that of the original tube b. It will also be noted that the upper and lower walls of this reduced oval section c are effectively braced against necking by the included bar II, and that the archlike formation of the sides of this oval section A is such as to render them self-sustaining.

After the tube b is reduced by passing it and the included bar I I through the non-circular orifice I2 in the manner above described, the tube may be returned to circularV form and loosened from the bar by any known or approved method. In.this instance this is accomplished by passing the tube and bar through a circular orice I3 in a second die I4. The primary function of the orifice I3 is to return the tube to true circular form. although it may also serve to effect a further slight reduction in the tube, the perimeter of the orifice I3 being substantiallyequal to or slightly less than that of the'oval tube section c. In any event, after passing through the die I4, the 'resulting circular section d of the tube is entirely free from the rod II and may be readily withdrawn therefrom.

For convenience, the two dies I0 and Il are lpreferably arranged so that the tube b and bar II may be passed through both on a single pass. During the pass the two dies are preferably spaced apart,`as indicated in Fig. A1, so as to permit the oval section c of the tube to bear upon the bar II for a material distance before enter- -ing the second die Il. However, to facilitate initial entry of the tube and bar into and through the second die, and to obviate the necessity of an objectionably long point on the leading end a of the tube and bar, the second die I 4 is preferably` adjustable into position adjacent the die III, as indicated in Fig. 4, in which position the pointed end a of the tube and bar may be readily projected through both dies into position to be gripped by the draw-head of the draw-bench.

During the draw stroke the die I0 is held stationary by appropriate stops I5, the die I 4 traveling with and on the tube until it engages its fixed stops I8, in which position it is thereafter securely retained by the stops I6 until the tube and bar have` passed through both dies.

In order to permit initial entry of the tube 'inte and through both dies, the leading end a l end of the bar.

Various changes may be made in the method and means hereinabove specifically described without departing from or sacrificing the advantages of the invention as deiined in the appende claims.

I claim:

1. The improved method of reducing tubing which comprises placing a round bar within the tubing, and pulling said bar and tubing through a non-circular die orifice having a perimeter materially less than the external perimeter of the entering tubing, the minimum clearance between said bar and the walls of said orifice being not materially less than the wall thickness of the entering tubing.

2. The improved method of reducing tubing I which comprises placing a substantially round bar Within the tubing, pulling the bar and tubing through a non-circular orifice having a perimeter materially less than the external perimeter. of

the entering tubing, theminimum clearance between the bar and walls of the orifice being not materially less than the wall thickness of the entering tubing, and pulling the bar and tubing through a substantially circular orifice to free the tubing from the bar.

3. The method of reducing tubing which consists in Vdrawing the tube while hot through an orifice having a perimeter materially less than the perimeter of the entering tube to determine the dimensions of the tube solely by tension and external confinement, and internally bracing the tube at peripherally spaced points therein to prevent collapse thereof upon emergence from the orice.

4. The method of reducing tubing which consists in drawing the tube while hot through an j orifice having a perimeter materially less than the perimeter of the entering tube to reduce the tube without imposing tube-shaping pressure against the interior surface of the tube, and bracing the tube at peripherally spaced points therein to prevent collapse Vthereof upon emergence from the orliice. l

5. The method of reducing tubing which consists in drawing the tube while hot through an orifice having a perimeter materially less than the perimeter of the entering tube to determine the dimensions of the tube solely by tension and external confinement, and simultaneously passing through said orice internally of and with said tube a bar dimensioned to contact the interior of said tube at spaced peripheral points upon emergence from the orifice to thereby brace the bar and having a perimeter materially less than4 the perimeter of the entering tube to reduce the tube and bring the same into contactwith said bar at spaced peripheral points without imposing tube-shaping pressure of the interior surface of the tube against said bar,\whereby said bar braces the tube against collapse upon emergence from the orifice.

7. The method of reducing tubing which consists in inserting within said tube a bar substantially smaller than the interiorbf the tube, and drawing the bar and heated tube through an orifice of different shape than said bar and having a perimeter materially less than the perimeter of the entering tube, the minimum clearance between said oriflce and said bar being substantially equal to the -wall thickness of the entering tube whereby saidv bar contacts the interior of said tube at spaced peripheral Points and braces said asvdses tube `against collapse upon emergence from the oritlce.

8. The method of reducing tubing which conl sists in drawing the tube while yhot through a.l

\ non-circular orifice having a perimeter matemuy mss than the perimeter of the entering tube to reduce the tube and determine the dimensions thereof solely by tension and external conilnement, and simultaneously passing through said of said tube at'spaced peripheral points and braces said tube against .collapse upon emergence from the oriilce.

11. The method of reducing tubing which consists in drawing the tube while hoi'I through a non-circular orifice having a perimeter mate- ,rially less than the perimeter of the enteringy tube tovdetermine the dimensions oi the tube solely by tension and external conilnement, in-` ternally bracing the tube against collapse upon emergence from the orice, and passing said tube through a circular orice to restore said tube to substantially circular shape.

12. The method of reducing tubing which consists in drawing the tube while hot through a non-circular orifice having a perimeter materially less than the perimeter of the entering l tube to reduce the tube without imposing tubesubstantially oval orice having a perimeter sub stantially less than the perimeter of the entering tube to determine the dimensions of the tube solely by tension and external connement, and

said tube and internally thereof a circular bar having a diameter substantially equal to the simultaneously passing through said orice with smallest internal diameter of the reduced tube v to thereby contact and support said tube at l spaced peripheral points and brace said tube against collapse upon emergence from the orifice.

k10. The method of reducing tubing which consists in inserting within said tube a circular bar of substantially smaller diameter than the interior of the tube, and drawing the heated tube and bar through a substantially oval orifice having a perimeter materially less than the perimeter of the entering tube, the minimum clearance between said oriilce and said bar being substantially equal to the wall thickness of the entering tube, whereby said bar contacts the interior shaping pressure against the interior surface thereof, bracing the tube against collapse upon emergence from the orice, and passing the reduced tube through a circular orice to restore its circular shape.v

V13. The method of reducing tubing which consists in inserting within the tube a circular bar having a diameter materially less than the internal diameter'of the tube, drawing the tube while hot and the bar simultaneously through a substantially oval orifice having a perimeter' materially less than the perimeter of the entering tube to reduce the tube andbring the same into contact withsaid bar at spaced peripheral points without imposing tube-shaping pressure of the interior surface of the tube against said bar,

lwhereby lsaid bar braces the tube against col lapse upon emergence from the orifice, and passing ,said tube and bar through a circular oriiice to free said tube from said barand restore said tube to substantially circular shape.

, SVEN WESTIN. 

